A large number of vacuum cleaners are known, whether for processing dust or liquids. Most vacuum cleaners very commonly rely on a rotating impeller structure, but other structures have been disclosed. Some vacuum cleaners that have been disclosed in the literature are as follows: U.S. Pat. No. 4,683,608 (Berfield et al.) for “Alternate blower outlet for vacuum cleaner” issued Aug. 4, 1987 to Shop-Vac Corp.; U.S. Pat. No. 6,499,385 (Protti) for “Hand vacuum pump with linear piston actuation” issued Dec. 31, 2002 to Innova Electronics Corp.; U.S. Pat. No. 5,788,463 (Chan) for “Manual vacuum producing system having pressure indicator” issued Aug. 4, 1998; U.S. Pat. No. 4,921,510 (Plooy) for “Vacuum cleaner system” issued May 1, 1990; U.S. Pat. No. 6,836,930 (Thur et al.) for “Airflow indicator” issued Jan. 4, 2005 to Royal Appliance Mfg. Co.; U.S. Pat. No. 6,058,561 (Song et al.) for “Vacuum cleaner suction apparatus” issued May 9, 2000 to Samsung Kwangju Electronics Co., Ltd.; U.S. Pat. Pub. No. 2003/0037408 (Park, LG Electronics Inc.) for “Suction head for vacuum cleaner” published Feb. 27, 2003; U.S. Pat. No. 4,363,156 (Leinfelt) for “Vacuum cleaner dust container having compressing means associated therewith” issued Dec. 14, 1982 to Aktiebolaget Electrolux; U.S. Pat. No. 4,508,550 (Berfield et al.) for “Air flow responsive outlet from tank of vacuum cleaner” issued Apr. 2, 1985 to Shop-Vac Corp.; U.S. Pat. No. 4,976,002 (Leonov et al.) for “Tube particle vacuum cleaner” issued Dec. 11, 1990 to Intel Corp.; U.S. Pat. No. 6,026,541 (Bailey et al.) for “Multi-purpose attachment tool for a hand-held vacuum cleaner” issued Feb. 22, 2000; U.S. Pat. No. 6,081,961 (Wang) for “Portable vacuum cleaner” issued Jul. 4, 2000; US 2003/0146631 (Stoev) published Aug. 7, 2003 for “Vacuum pet litter remover”; U.S. Pat. Nos. 4,820,315 and 4,723,969 (both to DeMarco) for “Vacuum loader and process for removing asbestos and other particulate material” issued Apr. 11, 1989 and Feb. 9, 1988 respectively; US 2005/0011036 (McCutchen) published Jan. 20, 2005 for “Ambient air backflushed filter vacuum.”
Also, U.S. Pat. No. 4,159,133 (Belanger) for “Flexible vacuum bellows” issued Jun. 26, 1979 to Air Products and Chemicals, Inc.; U.S. Pat. No. 5,899,653 (Brodine) for “Two-stage vacuum bellows” issued May 4, 1999 to Applied Materials, Inc.; U.S. Pat. No. 5,951,268 (Pottier et al.) for “Sperial vacuum pump having a metal bellows for limiting circular translation movement” issued Sep. 14, 1999 to Societe des Brevets P. Vulliez; U.S. Pat. No. 6,065,499 (Pless et al.) for “Lateral stress relief mechanism for vacuum bellows” issued May 23, 2000 to Eaton Corp.; U.S. Pat. No. 6,231,054 (Allen et al.) for “Elastomeric sliding seal for vacuum bellows” issued May 15, 2001 to Axcelis Technologies, Inc.
When a rotating impeller is used in a vacuum cleaner, the impeller must be rotated at a high speed to produce sufficient suction, and a byproduct is a high siren scream noise. Thus vacuum cleaners have been very noisy.
There have been many attempts to make vacuum systems somehow more quiet. See U.S. Pat. No. 4,120,616 by Dwyer et al. issued Oct. 17, 1978 to Breuer Electric Mfg. Co. (for “Vacuum cleaner-blower assembly with sound absorbing arrangement”); U.S. Pat. No. 4,987,824 by Shinohara et al. issued Jan. 29, 1991 to Nissin Kogyo Kabushiki Kaisha (for “Tandem-type vacuum booster with noise suppressing air passage”); U.S. Pat. No. 6,023,830 by Cole et al. issued Feb. 15, 2000 to Dana Corp. (for “Apparatus and method for installing a noise reduction structure within a vehicle driveshaft tube”); U.S. Pat. No. 6,779,228 by Plomteux et al. issued Aug. 24, 2004 (for “Quiet central vacuum power unit”); U.S. Pat. No. 5,502,869 by Smith et al. issued Apr. 2, 1996 to Noise Cancellation Technologies, Inc. (for “High volume, high performance, ultra quiet vacuum cleaner”); U.S. Pat. No. 6,804,857 by Olewiler, III issued Oct. 19, 2004 to M.D. Manufacturing, Inc. (for “Apparatus for dampening the noise of a vacuum cleaner”); U.S. Pat. No. 4,187,997 by Mosciatti et al. issued Feb. 12, 1980 (for “Vacuum control system for magnetic tape handler” where the elimination of belts, gears and high speed blowers is said to result in an unusually quiet system); U.S. Pat. No. 4,669,952 by Forsyth, III et al. issued Jun. 2, 1987 to Ametek, Inc. (for “Quiet by-pass vacuum motor”); U.S. Pat. Nos. 4,547,927 and 4,586,214 both by Berfield issued Oct. 22, 1985 and May 6, 1986 respectively to Shop-Vac Corp. (both for “Compact vacuum cleaner” said to maintain quiet conditions in spite of high speed air flow).
U.S. Pat. No. 6,014,791 (Nosenchuck) for “Quiet vacuum cleaner using a vacuum pump with a lobed chamber” issued Jan. 18, 2000 to SounDesign, LLC, instead of a traditional impeller, used a lobed (Wankel-type) vacuum pump. In his Background section, Nosenchuck mentioned but expressly taught away (˜col. 1, line 64+) from using a reciprocating piston structure, and taught using a lobed (Wankel-type) vacuum pump to avoid a traditional impeller.
Another aspect of vacuum cleaners is their suction performance. Conventional, commercially available centrifugal-impeller vacuum devices have suction performance (generally measured in inches of water-column, with the vacuum inlet sealed, to obtain maximum static suction) in the range of 40 to 145 inches. A typical household vacuum cleaner has suction of about 40-60 inches of water; a typical low cost shop-type canister style vacuum cleaner has suction of about 60-80 inches of water; a high performance shop and industrial vacuum cleaner has suction of about 100-145 inches of water. (It will be appreciated that suction measurement being expressed in terms of inches of water does not mean that the device is necessarily used for vacuuming water as opposed to vacuuming dust, etc.) At the top end of the vacuum suction performance hierarchy (i.e., 120-145 inches of water), the centrifugal-impeller conventional vacuum ‘head” will have two or three “stages,” which are cascaded together and typically driven by a common motor shaft, to obtain the suction performance. This is a costly and complex assembly of components.
Theoretically, on paper, the absolute maximum possible performance, a “hard” vacuum, would be about 407 inches of water at sea level in a “standard” atmosphere, using a “perfect” vacuum unit. However, a vacuum suction of 300 inches of water might be impossible to obtain using centrifugal-impeller schemes, and would certainly be prohibitively expensive, prohibitively complex, and would have minimal volume flow capability at such a high suction level. The cause of this difficulty is the mechanical “slip” or leakage inherent in the basic impeller scheme, whereby the motion of the air particles is not positively controlled. The air is not positively captured. Rather, the air is pushed in a manner very much like sweeping water uphill with a loose-bristle broom. When broom-sweeping rapidly enough, the water will move uphill, and will not easily fall back. Yet some of the water will “slip” or leak through the loose broom bristles, no matter how hard or how fast you sweep. Similarly, when vacuuming with an impeller device, some air molecules will always “slip” or leak past and flow around the impeller blades in a practical conventional centrifugal-impeller vacuum device, no matter how carefully it is constructed.
In a conventional impeller style vacuum device, the internal rotating part spins at a fast speed so that an air particle is accelerated out radially and eventually exits. Centrifugal vacuum pumps (also known as vacuum blowers) are compression suction devices. Inevitably the air particles in these conventional impeller style vacuum devices experience a non-negligible amount of “slip” because nothing is positively forcing air out. Various valving mechanisms have been attempted to keep “slip” under control, but without full success. “Slip” has not been overcome in impeller-style vacuum devices, and suction has not been as strong as would be wanted. For high volumes of air, air is at relatively low static suction, making delivery of high vacuum difficult because of the slip problem. The approach conventionally used has been a multistage approach, which has been difficult to implement and has not solved the problem.
Most shop vacuums are clean impeller pumps (as contrasted with a dirty impeller pump which moves something besides air). In household vacuuming, air is drawn through a large bag and then exhausted. Light weight motors can be used that drive the impeller relatively fast, as is needed, but along with the fast movement necessarily comes the high noise factor. However, slowing the impeller movement is unacceptable because sufficient working suction is then not provided.
Some positive displacement vacuum devices have been suggested over the years, but have not been able to be made to process enough air volume. For example, in household or industrial vacuum cleaning of carpets, a certain air volume is needed to entrain a particle in the air flow to get the particle released from the carpet (i.e., to overcome static forces, stiction, etc.). The conventional devices use a nozzle or the like, and there necessarily is a distance from the nozzle to the backing of the carpet by virtue of the structure of the carpet. In conventional devices, much air must be sucked in order to be able to entrain particles in the carpet. Conventional high vacuum devices generally only work on a very small section of carpet (such as when the wide suction implement is taken off a conventional vacuum cleaner, and a small nozzle is used instead).
In addition to the suction limitations of an impeller-style vacuum cleaner, the impeller structure, as has been mentioned is noisy (sometimes referred to as a “siren scream” caused by pulsations of sound by air pushed by impeller blades). The unmet demand for vacuum cleaner quietness continues. Impeller structures remain relatively noisy. Impeller-free structures have yet to be as successful as may be wanted for other requirements, such as suction and amount of material handled. Balancing the desired features of vacuum cleaners (such as suction, quietness, amount of material handled, etc.) remains an unsolved problem. For example, a high-suction, quiet vacuum is not yet known.